DCTCP is designed to address the TCP incast congestion in data center networks. But it may cause TCP timeout due to the lack of prompt packet loss detection, thus restricts the maximum number of concurrent senders. In this paper, an enhanced DCTCP called E-DCTCP is designed based on the notion of ECN. E-DCTCP composes of two phases, i.e. loss detection and backoff retransmission. In the loss detection phase, if any switch detects a packet (e.g. A) to be dropped, it stamps a dedicated ECN flag on A, and immediately routes A back to its sender. In the backoff retransmission phase, if a sender receives any backtracked packet A, it retransmits A based on a simplified binary exponential backoff algorithm. We show by simulations that E-DCTCP provides higher goodput and shorter flow completion time than DCTCP when the number of concurrent senders increases.